The long-term goals of the proposed program are to further the understanding of the mechanism of cellular immunity with an emphasis on lymphocyte mediators. These substances are elaborated by antigen or mitogen activated lymphocytes and are thought to play an important part in mediating cellular immunity of hypersensitivity. Our emphasis has been and will continue to be on one of these, migration inhibitory factor (MIF), which is measured by its ability to inhibit the migration of normal peritoneal macrophages out of capillary tubes and which appears to enhance the defense capacity of these cells. The specific goals of the propsoed work are: Furter investigation of the role of glycoporteins on the macrophage surface as part of the receptor site for MIF afd characterization of this receptor moiety and its relation to other macrophage membrane components, and Further investigation of the role of macrophage associated esterases as a possible control mechanism of the MIF macrophage interaction and characterization of these esterases.